The space Shuttle Transportation System provides man new opportunities for exploitation of space. The capability to economically place large payloads in orbit offers the chance to perform space missions that previously were impractical. Projects presently under consideration include the construction of a space station to provide permanent manned presence in space. The prospect of such a structure provides unparalleled challenges for developing extremely efficient structural concepts and new and unique ways to fabricate and assemble such a structure.
Realistically, any mission involving constructing large structures in space in the near future must be accomplished via the space shuttle. It is therefore advantageous to develop efficient structural concepts for maximum utilization of the shuttle payload bay and minimize the total number of flights required. Although the space shuttle represents an improvement in orbital payload capability, it is limited to a payload of approximately sixty-five thousand pounds in weight with a diameter of fifteen feet and a length of sixty feet. Such limitations must be taken into consideration.
Space station studies conducted by the aerospace community often depict space station concepts comprising several habitable pod clusters attached to long boom structures supporting solar panel wing-like appendages. A disadvantage of such concepts is the inherent low frequency of their structural arrangement. Small perturbations occurring from docking or maneuvering forces will cause the low frequencies of the booms and wing-like appendages to be dynamically excited requiring control systems to stabilize the structure. While such concepts provide an observation post for observing the earth or deep space and laboratories to perform zero-G experiments, they are not efficient as work platforms that can be used to construct and service large space vehicles for voyages to higher orbits and for interplanetary missions. Those space station configurations that do contain areas for payload storage of fabrication often place such areas in locations that are remote from the center of mass of the space station; therefore, if a payload is mounted on the structure, the mass and center of gravity of the space station will change and additional reaction control must be utilized to stabilize the station in its intended orbital attitude. To minimize the changes in gravity gradient torques and the overall dynamic characteristics that can occur when large masses, such as orbital transfer vehicles or satellites, are attached, removed or moved about, the large transient masses should be placed as near the center of mass as possible. Moreover, the demands of antennas and solar cells for accurate positioning and the requirements of adequate stiffness to avoid undesirable structural distortions require consideration.